JPS6347322Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This invention relates to the structure of a variable regulating valve that can remove scale adhering to a flow control valve installed in a water supply pipe to a water wall pipe of a boiler, particularly a supercritical pressure boiler, even during operation of the boiler. Since once-through type boilers are used for high-temperature, high-pressure boilers, especially supercritical pressure boilers, it is necessary to prevent scale formation due to trace components contained in the feed water.
It is regulated to a value on the order of ppb (unit of 1 mg of solute in 1 ton of water) (for example, about 10 ppb Fe), which is even stricter than ppm order. Further, the water wall pipe is constituted by a plurality of unit water wall groups in which a plurality of unit water walls connecting an inlet side header and an outlet side header are arranged along one flow. This is schematically shown in FIG. 1 and will be explained. Water is supplied to the water wall pipes via a water wall inlet connecting pipe 2 that branches from the main water supply pipe 1, and a variable orifice valve (hereinafter referred to as VO (referred to as valve) 3a,
3b, 3c, 3d to each water wall inlet header 4a,
4b, 4c, 4d and water walls 5a, 5b, 5
c, 5d, then water wall outlet header 6a, 6b, 6
c, 6d, and are sent out from the water wall outlet connecting pipe 7. In this case, the flow rate of water flowing through the VO valves 3a, 3b, 3c, and 3d will vary depending on the conditions of the burner arrangement of the boiler, the flow of high-temperature combustion gas, the shape of the bent flow path of the pipe, and the heat transfer load. Also these VO
Damage to the water wall pipe can occur if the resistance of the valve is not adequate, i.e., due to the water supply flow rate to that pipe wall. For this reason, the heat absorption amount in the furnace is mainly distributed by adjusting the VO valve. As this VO valve, a Y-globe type variable orifice valve (YVO valve), a partial cross section of which is shown in FIG. 2, has conventionally been used. However, in a supercritical pressure boiler, even if the feedwater content is strictly controlled on the order of ppb, extremely small amounts of iron in the feedwater concentrate and adhere to the vicinity of the throat of the VO valve (indicated by short diagonal lines in Figure 2). During operation and periodic inspections, it was found that this increased the system loss of the entire boiler. This scale build-up is accompanied by a rise in pressure, and the water supply pressure exceeds the "water supply piping design pressure" during an operating period of 3 to 6 months, and the plant must be shut down and scale removed by chemical cleaning or valve disassembly each time. necessitated a temporary measure. However, from the viewpoint of the target of continuous operation of the plant for two years and energy saving measures, it is necessary to prevent scale accumulation or to automatically remove the accumulated scale using a flow control valve with a self-cleaning variable orifice (hereinafter referred to as a self-cleaning VO valve). ) development has been strongly requested. This idea was taken a step further because it was predicted that scale accumulation would still occur during long-term operation even with the scale self-cleaning variable regulating valve proposed by the inventors (Japanese Patent Application Laid-open No. 170975/1983). The present invention also aims to propose a structure for a variable regulating valve that mechanically removes scale deposited in the valve orifice (opening) by operating the valve body from the outside, thereby further extending the continuous operation period of the boiler. In short, this invention is characterized by a variable adjustment valve equipped with an orifice scale removing member, in which the valve seat is provided with a protrusion member that protrudes from the inner wall of the valve seat and has a surface facing the upper edge of the orifice. First, we will consider why such small amounts of impurities are usually deposited near the evaporation point of the evaporation tube, but why do they deposit in the VO valve where the water supply speed is over 20 m/s? There is a need. Table 1 shows the results of scale component analysis performed for this study. That is, it was found that Fe ₃ O ₄ was the main component.

[Table] Figure 3 shows a partial cross-section of the variable orifice valve (VO valve) proposed earlier by the inventors, and Figure 6 shows a cross-section and enlarged view of the main parts of the valve. A valve seat 9 is screwed and fixed to the VO valve 8, and a valve body 10 is slidably positioned inside the valve seat 9. The bottom of the valve body 10 is open, the lower part is cylindrical, and one or more openings 11 are provided in the side wall 10a. A perspective view thereof is shown in FIG. Further, the upper outer surface of the valve body 10 has an inner surface on which it can slide, and the opening 1
A space 12 that temporarily receives the water supplied from 1.
The cage 13 provided with the valve seat 9 is held by the flange 14 directly or via a presser 15 so that its lower end is in contact with the upper surface of the flange, and the cage 13 and the valve seat 9 form a cylindrical body. This cage 13 is shown in Figure 5 (perspective view of the cage).
As shown in the figure, a plurality of holes 13a and 13b are provided to prevent the high-speed water supply flow ejected from the opening 11 under flow control from directly colliding with the VO valve body and damaging it due to erosion. The supplied water flows in from the direction shown by the left arrow of the VO valve 8, flows upward from below the valve body 10, bends through the opening 11, flows into the flow space 12, and flows into the flow space 13 of the cage 9.
a, 13b, flows in the direction of the arrow on the right side of the drawing, enters each water wall inlet header, ascends each water wall pipe, and flows to the water wall outlet connecting pipe. Figure 7 shows the first VO valve used experimentally, AA of the one shown in Figure 3.
A cross section is shown. The edge surface of the opening 11 is an opening with a simple cross-sectional shape that is perpendicular to the outer circumferential surface of the valve body as shown. In this case, the scale deposit 14 has an annular shape and a "cylindrical fish cake" cross section in accordance with the shape of the opening having the lower wall thickness T of the valve body 10 at its base, as shown in FIG. 8, and the scale deposit has grown. Some of the openings were blocked. According to the survey, the porosity is approximately 60
%, the breaking strength was approximately 0.32 kg/mm ² . There was also no evidence of corrosion on the adhesion surface. For this reason, the cross section of the opening must be designed so that the flow is smooth and condensed, and the area that forms the basis of the scale must be reduced. In addition, the shape of the VO valve opening (orifice) 111 is approximately 5 mm, with the top shaped like an inverted V, as proposed by the inventors.
The rectangular opening was effective in preventing scale accumulation, resulting in a small amount of scale growth as shown in FIG. A square aperture with a horizontal top such as in FIG. 13 did not produce favorable results. Given that such scale accumulation is unavoidable in variable regulating valves used in supercritical pressure boilers, there is a strong demand for proposals for valve structures that can remove scale without stopping boiler operation. It is a place. Figures 14 to 16 show the structure of a variable regulating valve with an orifice scale removing member for a rectangular orifice with a flat orifice top, as proposed by the inventors. As shown in FIG. 13, the scale 16 is mainly attached to the upper edge of the orifice, so when mechanical force is applied to it, the scale cracks and can be washed away by the high speed boiler feed water flow. For this purpose, a protrusion member 15 or 17 is provided on the upper edge of the two divided valve seats 109a and 109b at a location corresponding to the orifice. Dividing the valve seat into two is adopted as a structure that requires assembly in order to position the protruding member 15 within the opening. FIG. 17 shows the scale 16 attached to the orifice, and FIG. 18 shows the scale 16 just before it comes into contact with the projection member 15 and is bent and washed away. The upper surface of the protruding member 15 is formed into a slope 17a that is inclined toward the valve seat axis, thereby making it easier to bend the scale. In order to prevent burnout of the water wall, it is preferable to carry out the scale removal operation at a low load when the burner of the water wall pipe assigned to the valve is temporarily extinguished or when the boiler is stopped for a short time. The valve seat is provided with a bolt hole 18 for assembling the divided valve seat, and an assembly bolt 19 is provided in the valve seat.
is used. As a second embodiment, when the top edge of the orifice is in an inverted V shape and has a pentagonal shape (FIG. 21), the protrusion member 17 extends upwardly from the upper surface of the valve seat 109b' and the valve as a whole is It becomes a protruding member protruding from the inner surface on the seat axis side, and its perspective view is shown in No. 20.
It will be as shown in the figure. By implementing this invention, even if scale adheres to the orifice of the variable regulating valve, the valve body 10 can be lowered to bring the scale and the protruding member into contact, making it easy to remove the scale, allowing continuous long-term operation of the boiler. This has the effect of

[Brief explanation of the drawing]

Figure 1 is a diagram schematically showing the water supply system to the water wall tube of a supercritical pressure once-through boiler, and Figure 2 is a diagram showing a conventional Y-type VO
Figure 3 is a partial cross-sectional view of the VO valve, Figure 4 is a perspective view of the valve body 10, Figure 5 is a perspective view of the cage, and Figure 6 is a diagram showing the cage and the position of scale adhesion. An enlarged cross-sectional view of the valve body and the vicinity of the valve seat, Figure 7 is the third
Figure 8 is a sectional view taken along line A-A of the valve body shown in Figure 7.
C sectional view, FIG. 9 is a BB sectional view of the valve body in FIG. 6, FIG. 10 is a DD sectional view in FIG. 9, FIG. 11 is an enlarged view of the opening in FIG. 10, and FIG. 12 13 is a drawing showing scale adhesion to the top of the opening, FIG. 13 is a drawing showing scale adhesion to a rectangular opening with a flat top, and FIG. 14 is a longitudinal sectional view of a variable regulating valve showing the first embodiment of this invention. Fig. 15 is a partial view taken along the line FF in Fig. 14 showing the relationship between the orifice with a flat upper edge and the projection member 15, Fig. 16 is a sectional view taken along the line E-E in Fig. 14, and Fig. 17 is a scale view. 18 is a drawing showing a state in which the protruding member 15 and the scale are in contact and the scale is removed; FIG. 19 is a perspective view of the two-split valve seat 109a; Figure 20 shows protruding member 1 for pentagonal orifice.
Perspective view of the two-part valve seat 109b with 7, No. 21
The figure is a partial view showing the relationship between the pentagonal orifice 111b and the projection member 17. 15, 17... Projection member, 109a, 109
b, 109b'...Split valve seat, 19...Assembling bolt.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. A valve seat 9 provided in the valve body, and a plurality of holes 13 in the wall of the enlarged-diameter cavity 12 below the valve seat.
A, 13b is pressed by a cage 13 to form an integral cylindrical body, and a valve body 10 having one or more openings 11 on the wall surface of a cylindrical space with an open bottom end is inserted in the axial direction within the cylindrical body. In a high-pressure globe-type VO valve that changes fluid flow resistance by sliding displacement, a variable adjustment valve with an orifice scale removal member is provided, in which a protrusion member is provided on the valve seat, protruding from the inner wall of the valve seat and having a surface facing the upper edge of the opening. . 2 Utility Model Registration Scope of the Claim The variable regulating valve with an orifice scale removing member according to claim 1, wherein the surface of the protruding member facing the upper edge of the opening is an inclined surface. 3. A variable regulating valve with an orifice scale removing member according to claim 1 of the utility model registration, in which a protruding member having a slope facing an opening having a chevron-shaped upper edge is provided on the valve seat.